(Don’t) get your ass to Mars!

This post is the first of many, many posts on the human exploration of Mars.

Why we can’t get there from here

I have great sympathy for the principle of human exploration of Mars and even potential colonization in the future. But frankly the belief that we can transport humans to Mars, have them land safely, conduct experiments and exploration and safely return using current or near future technologies is rooted in a quasi-religious belief system which I call “hard science fiction” and is the meta-theme of this blog.

Now this article isn’t saying that getting to Mars is impossible, but in reality things can go wrong (just ask the crew of Apollo 13) and aborting a mission to Mars is one of the things that needs to be considered.

I love the question posed (by someone called Joan):

Could Mars One turn back en route if they had regrets? Reality would set in seeing[our] beautiful blue planet get smaller while they head towards a dead toxic planet or if radiation/solar winds [were] to wildly [exceed] safe levels.

Now that’s a question that needs to be answered.

Not because crews might have regrets, because that’s what an astronaut training program would be geared to filter out, because the last thing you’d want is a crew member who goes into a psychotic fit en route to Mars and must be (physically and/or chemically) restrained. In a module as small and claustrophobic as a Mars module, that would cause a mission abort all on its own.

But Mars is (as far as we know) dead and is definitely toxic, so this is not a trivial question.

…when we talk about a manned mission to Mars, there are a few different plans out there. The most optimal one for a one-way trip to Mars, for those of you wondering, that minimizes both flight time and the amount of energy needed, involves simply timing your launch right.

There’s an approximately two-month-long launch window that occurs every 780 days, where Earth overtakes Mars in its orbit, where the time-of-flight to Mars is only about 243 days: 8½ months. The tough part is, once you’re on your way, you’re moving at incredible speeds, and you’re not carrying a lot of fuel on board to correct your trajectory.

Why not?

Because every extra kilogram of fuel you carry means it’s that much more expensive to launch your rocket, and it also means there’s that much less storage room and capacity to devote to food, water and other supplies. As a consequence, there’s that much less room-for-error. If the infamous Apollo 13 mission hadn’t planned on landing on the Moon, lifting off to reconnect with the command module, and return to Earth, they never would have had enough fuel to make the necessary course corrections to get themselves back home.

That optimal strategy is called the Hohmann Transfer which is the one diagrammed above, and every other option sub-optimal because it would require more fuel and hence more mass would have to be sent up from the Earth’s surface in the first place.

If you’re on your way to Mars, and you all-of-a-sudden decide you have to get back to Earth, using your on-board fuel to change your course and head back home simply wouldn’t be an option: fuel-wise, it’s too expensive. In other words, Joan, to answer one of your questions, if it was radiation that was killing you — something we may have to worry about, as we’ve never had humans spend large amounts of time this far away from Earth’s protective magnetic field — you’re simply going to die.

So, once you’ve broken Earth’s orbit at the beginning of the Hohmann transfer then you’re committed – you won’t have enough fuel to turn around the way they do in the movies.

But if time wasn’t an issue, because you had the food, water and supplies you needed to survive, and you had all the fuel you needed to get yourself to Mars, you’d have a chance to return home. This could be of vital importance for a mission like the one you allude to — Mars One — because the way it’s currently planned, it’s a suicide mission.

And it is – right up front, Mars One is a one-way trip to a dead, toxic planet. Once you’re on that transfer, you’ll never see Earth again.

Unless you’re in just the right orbit where this happens:

So if you were on your way to Mars and wanted to come back, your only realistic option, with the expected amount of fuel you’d outfit your spacecraft with, would be to use the red planet’s gravity to turn yourself around back towards Earth, which would result in a total round-trip time of around 400-to-450 days. Without any interplanetary infrastructure, that’s the best you can hope for.

But all of the above rests upon a key assumption – that there is no infrastructure on Mars.

Why would that be the case?

Mars Direct

In Robert Zubrin’s book “The Case for Mars”, he advocates a mission strategy called “Mars Direct” which envisages a series of missions to colonize, explore and return samples (and humans) from the surface of the planet.

The first mission, which Zubrin dubs “Ares 1”, a robotic mission is sent first which sends a habitation module, a nuclear power plant, a chemical plant and a return vehicle to Mars.

The whole lot lands on Mars (a heroic assumption, given the poor record of Mars landers), where the chemical plant uses water in the soil of Mars which is heated by the nuclear power plant and then cracked into hydrogen and oxygen, which are then used to fuel the return vehicle and the habitation module (the “Hab”).

Then when all is signalled ready by the robotic Ares 1, the human part (“Ares 2”) lifts off, knowing that at the very least, the astronauts can abort either directly as shown above, or to the surface of Mars.

There’s at least one problem with that strategy: we don’t have the technology to land humans safely on Mars